Effects of Photobiomodulation on the Innate Immune System of Neonates and Infants Diagnosed With Acute Respiratory Sintitial Virus Bronchiolitis - Randomized Controlled Trial

Acute Viral Bronchiolitis (AVB) is the most common disease of the lower respiratory tract in children, being one of the major causes of hospitalization in children under two years of age, especially in winter. It is characterized by inflammation, edema, and necrosis of cells of the small airways epithelium, with increased mucus secretion and bronchospasm. Among the most common pathogens for the development of AVB are rhinovirus, influenza A and B, parainfluenza, metapneumovirus, adenovirus, however, the most common and responsible for 70% of AVB in children under two years of age is respiratory syncytial virus (RSV). RSV is highly contagious and infectious, accounting for 2-3% of the hospitalization of infected children, and there is a seasonal variation in RSV infection levels, which are higher during the winter in temperate regions, and this occurs because low temperatures and high humidity favor the proliferation of the virus.

RSV is transmitted through the air in contact with the nasal epithelium, mouth, eyes, or contaminated surfaces, and the incubation time is three to eight days. As soon as the virus reaches the nose or mouth, it begins to infect the epithelial cells of the upper respiratory tract, then progresses to the lower airways reaching the bronchioles where it replicates more easily, thus developing bronchiolitis. Inflammation and obstruction of the bronchioles then occurs, resulting in reduced airflow in the small caliber airways, altering the ability to exhale, which leads to hyperinflation, increased mucus production, atelectasis and wheezing. Immunopathology occurs through the expression of pro-inflammatory cytokines with subsequent perivascular and peribronchial infiltration of mononuclear cells, mostly neutrophils and lymphocytes, triggering an unbalanced response between T helper cells 1 and 2.

In addition to AVB, RSV infection can lead to pneumonia in addition to the possibility of later development of wheezing and asthma, so there is growing concern about how RSV infections in the first months of life can lead to the development of chronic lung diseases. in addition to being considered the second pathogenic agent causing death in children under one year of age.

The inability of the innate immune system of neonates and children to fight RSV infection and its serious consequences makes the development of new prevention and treatment strategies a priority.

To meet this need, notable advances have been made in recent years in relation to low-level laser PBM applied to lung diseases. PBM is a non-invasive, adverse-effect-free, accessible, and well-tolerated resource for patients diagnosed with pulmonary diseases such as chronic obstructive pulmonary disease, COVID-19 and asthma. Many effects are attributed to PBM and one of the main ones is its antioxidant and anti-inflammatory effects at the cellular level. From the penetration of the photon into the tissue where it interacts with intracellular molecules and initiates a series of changes in its functioning, including membrane permeability and cellular metabolism, regulating antioxidative defenses and reducing oxidative stress.